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Re: Driving headphones at high peak levels
> Choose a USB sound card with "better" specifications The
> USB sound cards that I have seen have output impedances
> of around 50 ohms or higher, making them unsuitable for
> driving low impedance phones, so a low-output-impedance
> USB sound card with decent maximum output would be one
> solution
I have tested several USB sound cards. The hands-down
winner for low output impedance (2 ohms) can deliver nearly
1.5 Vrms into 100 ohms. I especially like it because it
has no hardware controls on the unit that can get
accidentally changed in a lab setting. It has pretty good
specs in most other respects as well. See
the Comparison Table under "Sound Card Perfomance Tests" at
<http://www.daqarta.com/dw_gguu.htm>
The unit is based on the CM6206 chipset and is sold by
various suppliers. I got mine from HDE through Amazon.
Search for "5.1 channel USB sound" and look for a picture
that matches the one for "5.1 Channel CM6206 USB" on the
link above.
I just did that and found HDE's price has jumped up to
US$16.95... it was under $15 when I bought mine!
The only drawback I've encountered is that the mini-USB
connection on the back of the unit can loosen up... very
annoying in the middle of a test. I've temporarily
resolved this by some selective crimping, but a better
solution would be to remove the chassis and cable
connectors and hard-wire the USB cable to the unit.
Best regards,
Bob Masta
==================
On 7 Dec 2014 at 13:29, Bob Carlyon wrote:
> Dear list, I am involved in a project where we are play
> some pulsatile stimuli to listeners who may have a
> hearing loss. To do so we need to produce high peak
> levels in order to obtain sufficient loudness. The test
> will be run in different clinics worldwide, which means
> both that we can't choose an expensive solution, and
> that, at least preferably, we should be using USB
> devices - although I realise that the voltage provided
> by the USB will impose some limitations.
>
> I would be grateful for suggestions on how to maximise
> the audio output, and list below the general options &
> limitations as I see it
>
> Choose a sensitive transducer At present we are using
> Sennheiser HD650s which produce about 106 dB SPL/V for a
> 1-kHz sinusoid. In a recent post Mike Stone mentioned
> the HDA200 which produces 117 dB SPL/V, but that is very
> expensive; does anyone know of cheaper headphones that
> are also very sensitive? Another option is to use insert
> earphones such as the Etymotic ER 5. However the highest
> input impedance these come in is 50 ohms, which is
> similar to the output impedance of the USB sound cards I
> have tried (see below)
>
> Choose a USB sound card with "better" specifications The
> USB sound cards that I have seen have output impedances
> of around 50 ohms or higher, making them unsuitable for
> driving low impedance phones, so a low-output-impedance
> USB sound card with decent maximum output would be one
> solution The two cards that I have been calibrating
> differ by more than 8 dB in the maximum output they can
> produce into a 300-ohm load without clipping - the
> winner being the Roland Quad capture at a peak value of
> approx.. 2.6V. If anyone knows of a USB sound card that
> would exceed this, or even match it at a cheaper price
> (The Roland is about UK£150, so say US$225) I would be
> glad to hear of it
>
> Use a separate headphone amplifier Does anyone have
> experience of relatively inexpensive(say < US$150)
> headphone amps? As mentioned above something USB driven
> would be ideal, but maybe at a pinch we could use
> something driven by a 12V power supply using a mains
> adaptor. One option (just gleaned from the internet) is
> the ART headamp 4, but I have no experience with this
> and so if anyone has calibrated any such device and has
> suggestions again I'd be grateful
>
>
> I'd be happy to collate responses and post them to the list
>
>
> Cheers
>
> Bob
>
>
> Dr. Bob Carlyon
> Deputy Director
> MRC Cognition & Brain Sciences Unit
> 15 Chaucer Rd.
> Cambridge CB2 7EF
> England
> Tel: +44 (0)1223 355294
> Fax: +44 (0)1223 359062
> www.mrc-cbu.cam.ac.uk<http://www.mrc-cbu.cam.ac.uk/>
> See also the
> Cambridge Hearing Group<www-hearing-research.eng.cam.ac.uk/Main/WebHome>
>
>
Bob Masta
D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!